This invention relates to an improved electroplating apparatus of the type which utilizes a brush to apply a plating solution to selected regions of parts being plated.
A variety of electroplating approaches have been used in the past, including immersion or dipping of the parts to be plated in a plating solution, spraying of the plating solution onto the parts, and transporting plating solution to the parts with a tool (often called a brush) which includes an absorbent material positioned to contact the parts. This last approach is generally referred to as brush plating.
A number of early approaches to brush plating used a chamber into which a plating solution was pumped. An absorbent applicator was used to transport the plating solution from the chamber to the part being plated. For example, Snyder British Patent No. 18,643 shows in FIGS. 5-7 devices which use tufts of bristles to transfer plating solution to large surface areas of the parts being plated. Similarly, Thomas U.S. Pat. No. 2,540,602 shows in FIG. 4 an electroplating device which uses a pad of cotton or glass fiber to transfer plating solution from the device to the part, and Icxi U.S. Pat. No. 3,637,468 shows in FIG. 7 a similar device. See also the oscillating chamber and pad of Macula U.S. Pat. No. 3,751,343 (FIG. 2) and the rotating chamber and pad of Norris U.S. Pat. No. 4,304,654 (FIGS. 2 and 3).
Though the devices described in these patents use brush type applicators, none is well suited to the precise application of plating solution only to small, predetermined regions of the parts being plated.
Palnik U.S. Pat. No. 4,452,684 describes another prior art brush plating device which includes a central conduit that defines an array of openings along its length. The conduit is surrounded by an annular tube of a porous, hydrophobic plastic such as polypropylene, which is in turn surrounded by a felt covered platinum screen. The platinum screen is used as the anode in plating operations, and the parts to be plated are guided along the side of a stationary brush in contact with the felt. A plating solution is pumped into the conduit and flows via the openings and the pores in the body, through the screen and into the felt, from which it is transferred to the parts. In the Palnik device the brush is shaped as a generally convex surface which is not well suited for plating small regions of the parts. Because the arrangement of the screen and the felt, a sufficiently large snag or tear in the felt can create a short circuit between the screen and parts to be plated.
Tezuka U.S. Pat. No. 4,655,881 describes another brush plating method which uses a brush made up of an anode covered with a sleeve of an absorbent material such as a non-woven fabric. In one form the brush is dipped into a bath of plating solution and then moved into contact with the part. When the brush becomes depleted of plating solution, it is again dipped into the bath. In another form the brush defines a spiral fin which contacts the part, and the brush is rotated in a bath of plating solution to dip each section of the fin repeatedly into the bath. Both of these approaches require that the brush be moved into and out of the bath in order to continue the plating process. The need to move the brush increases the mechanical complexity of the plating apparatus. As with the Palnik device described above, any tear or snag in the non-woven fabric over the anode creates the potential for an electrical short circuit between the anode and the parts being plated.
The present invention is directed to an improved brush plater and components thereof, which are well suited to high precision plating of small regions of the parts being plated, and which are well adapted for use in a continuous process without requiring movement of the brush.